Rising Temperatures May Fuel the Spread of Dangerous Fungal Infections

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Fungi have always been part of the Earth's complex biological fabric. From the mold on stale bread to the mushrooms dotting forest floors, fungi exist in a broad spectrum of forms. Many are harmless, even beneficial, used in medicines, food production, and soil health. However, a darker side of this kingdom is emerging with alarming urgency: the rise of pathogenic fungi that threaten global health. With the planet heating up due to climate change, scientists are constantly warning that fungal infections—already responsible for millions of illnesses and up to 2.5 million deaths annually—are poised to become more widespread, more resistant, and more difficult to treat.

Understanding the Fungal Kingdom:

Fungi differ significantly from bacteria and viruses. They are eukaryotic organisms, meaning they share more cellular similarities with humans than microbes do. This makes them particularly hard to target with drugs, as treatments that harm fungi often harm human cells too. Moreover, fungal infections can range from superficial (like athlete's foot) to life-threatening systemic infections such as invasive candidiasis and cryptococcosis. The problem becomes even more severe for people with weakened immune systems, such as cancer patients, those living with HIV/AIDS, and organ transplant recipients, who are particularly susceptible to these infections.

Over the past few decades, a few key fungal pathogens have become well known in the medical world: Candida auris, Aspergillus fumigatus, Cryptococcus neoformans, and Histoplasma capsulatum, among others. These fungi are opportunistic, resilient, and increasingly resistant to antifungal treatments. In this context, the warning that global warming is turbocharging the spread and virulence of such pathogens has sent ripples through public health communities.

Climate Change: A Catalyst for Fungal Evolution:

Fungi historically have been limited in their capacity to infect humans due to a fundamental biological reason—temperature. Most fungi thrive in cooler environments, and the average human body temperature of around 37°C acts as a natural defense. However, as the planet warms, fungi are adapting to higher temperatures. This evolutionary pressure allows them to tolerate and survive in environments previously inhospitable to them, like the human body.

This adaptation could be best understood through the example of Candida auris. First identified in 2009 in Japan, C. auris has since become a global health concern due to its multidrug resistance and ability to survive on surfaces for extended periods. Scientists believe that its emergence may be linked to rising global temperatures, allowing it to breach the thermal barrier that typically protects humans from fungal infections. What’s more worrying is that this may just be the beginning. As fungi across the globe evolve under the selective pressure of heat, many more may acquire the capacity to cause disease in humans.

In nature, the arms race is relentless. Fungi are undergoing natural selection to survive not just heat, but also arid conditions, UV radiation, and the presence of antifungal chemicals used in agriculture and medicine. When these fungi enter human systems—either through the lungs, skin, or digestive tract—they may be more aggressive, more resistant to existing drugs, and more difficult to eradicate.

Geographic Spread and Environmental Disruption:

Climate change does not act in isolation. It catalyzes a series of events that disrupt ecological balances and facilitate the spread of diseases. As global temperatures rise, previously temperate regions are becoming warmer and more humid—ideal conditions for fungi to grow. This allows pathogens like Histoplasma and Coccidioides (responsible for Valley Fever) to spread beyond their traditional geographic zones.

In the United States, for instance, Valley Fever was once confined to arid areas in the Southwest. However, cases are now being reported in northern states as warming allows the fungus to thrive in new soils. Similarly, Cryptococcus gattii, once limited to tropical climates, has been found in the Pacific Northwest of Canada and the U.S., causing fatal infections even in healthy individuals.

Deforestation, urbanization, and increased human contact with wildlife also play critical roles. As natural habitats are destroyed, both humans and fungi are displaced, often leading to new interactions and transmission routes. Fungal spores can travel through the air, settle in soil or water, and lie dormant until the right conditions—like a warm, humid environment—activate their pathogenic potential.

The Burden on Public Health Systems:

Fungal infections are notoriously underdiagnosed and underreported. Unlike bacterial or viral diseases, fungal infections often fly under the radar, especially in low-resource settings where diagnostic infrastructure is lacking. This means that the real burden of fungal disease is likely far greater than current estimates suggest.

Antifungal resistance further complicates the problem. The overuse of antifungal agents in both agriculture and medicine has led to the emergence of drug-resistant strains. Due to widespread agricultural use, Aspergillus fumigatus, a common mold found in soil and decaying vegetation, has developed resistance to azole antifungals. When inhaled, it can cause invasive aspergillosis, a serious infection with high mortality rates.

Hospitals are seeing more patients infected with fungi that are resistant to multiple classes of antifungal drugs, leaving doctors with limited treatment options. The rise of Candida auris, which can resist most first-line treatments, has prompted some healthcare facilities to isolate infected patients and increase sanitation protocols, reminiscent of the early days of MRSA outbreaks.

Moreover, no vaccine is currently available for any human fungal pathogen. Treatment and prevention are thus solely reliant on antifungal drugs and infection control measures, both of which are becoming increasingly ineffective.

Vulnerable Populations at Higher Risk:

Not all populations face the threat of fungal infections equally. Immunocompromised individuals, such as those undergoing chemotherapy or living with chronic conditions, are most vulnerable. But with rising air pollution, worsening malnutrition, and increasing poverty—especially in developing countries—many more people are becoming immunocompromised or otherwise susceptible.

Furthermore, climate-related disasters such as floods, hurricanes, and wildfires can worsen the situation. Floodwaters can spread fungal spores in water-damaged buildings, leading to a rise in respiratory infections such as mucormycosis, famously dubbed “black fungus,” which spiked during the COVID-19 pandemic in India. Similarly, dust storms caused by drought can aerosolize spores of Coccidioides, increasing the risk of inhalation.

These fungi do not discriminate but tend to hit the poor and underserved the hardest—those with limited access to healthcare, poor housing, and inadequate nutrition. For countries already grappling with infectious diseases like tuberculosis, HIV, and malaria, the rise in fungal infections adds another layer of strain to overstretched health systems.

Surveillance, Research, and Global Preparedness:

The urgency of the fungal threat is not matched by global preparedness. Fungal diseases have historically received less attention, funding, and research compared to bacterial and viral diseases. This is now starting to change, albeit slowly. In October 2022, the World Health Organization (WHO) released its first-ever list of fungal priority pathogens, highlighting 19 fungi that pose the greatest threat to public health. The list calls for increased surveillance, research funding, and innovation in diagnostics, treatments, and vaccines.

More research is also needed to understand how climate change is altering fungal ecology. Genomic surveillance, environmental sampling, and epidemiological modeling can help track fungal evolution and predict future outbreaks. Investment in new antifungal drugs is critical, as the current pipeline is dangerously limited.

Education and awareness must also be part of the response. Clinicians should be trained to recognize and manage fungal infections, particularly those that present with symptoms similar to more common conditions like bacterial pneumonia or tuberculosis. Public health campaigns should also focus on high-risk populations, promoting early diagnosis and preventive strategies.

Holistic Response:

Tackling the rising threat of fungal infections requires a multifaceted approach. First, we must acknowledge the intersectionality of climate change, health, and socioeconomic inequality. Combating fungal diseases is not just about developing new drugs—it’s about improving living conditions, strengthening healthcare infrastructure, and protecting the environment.

Policymakers must integrate fungal threats into national health plans and climate adaptation strategies. Cross-sector collaboration between environmental scientists, epidemiologists, clinicians, and community organizations will be essential. We must also reduce reliance on antifungal agents in agriculture and promote responsible use in clinical settings to curb resistance.

Finally, the global health community needs to treat fungal infections with the same urgency as other emerging threats. Much like how the world mobilized resources to combat HIV/AIDS, Ebola, and COVID-19, a similar mobilization is needed for fungal pathogens. Only then can we stay ahead of this quiet, creeping epidemic.

"The time to invest in fungal research, surveillance, and healthcare resilience is now, not when it’s too late. With temperatures rising and fungal threats growing, our response must be swift, science-driven, and global. The health of future generations depends on it".

Citations:

• Brown, G. D., Denning, D. W., & Levitz, S. M. (2012). Tackling human fungal infections. Science, 336(6082), 647-647.

  Casadevall, A., Kontoyiannis, D. P., & Robert, V. (2019). On the emergence of Candida auris: Climate change, azoles, swamps, and birds. MBio, 10(4).
• Garcia-Solache, M. A., & Casadevall, A. (2010). Global warming will bring new fungal diseases for mammals. mBio, 1(1).
• Gorris, M. E., Cat, L. A., Zender, C. S., Treseder, K. K., & Randerson, J. T. (2021). Coccidioidomycosis dynamics in relation to climate in the southwestern United States. GeoHealth, 5(6).
• Robert, V. A., & Casadevall, A. (2009). Vertebrate endothermy restricts most fungi as potential pathogens. Journal of Infectious Diseases, 200(10), 1623–1626.
• GAFFI. (2020). Global Action Fund for Fungal Infections Annual Report.
• Singh, A. K., Singh, R., Joshi, S. R., & Misra, A. (2021). Mucormycosis in COVID-19: A systematic review of cases reported worldwide and in India. Diabetes & Metabolic Syndrome: Clinical Research & Reviews, 15(4), 102146.
• UNAIDS. (2023). Global HIV & AIDS statistics — Fact sheet. https://www.unaids.org/
• Rising temperatures could spread deadly fungus, experts warn, and other health stories: https://www.weforum.org/stories/2025/05/climate-change-spread-fungal-disease-and-other-health-stories/

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